As reported in Wired, Bransfield outfitted a cat collar with a Spark Core chip loaded with his custom-coded firmware, a Wi-Fi card, a tiny GPS module, and a battery.

The customized collar allowed Bransfield to map all the Wi-Fi networks in the neighborhood, which could also be done by a home intruder or a person intent on stealing a home’s Wi-Fi.

The project was jokingly entitled “War Kitteh,” and Branfield’s presentation at last weekend’s DefCon hacker conference in Las Vegas was entitled “How to Weaponize Your Pets.”

Bransfield says his goal wasn’t to create dangerous house pets, but to make users aware of privacy issues and entertain the group’s hacker audience.

“My intent was not to show people where to get free Wi-Fi,” says Bransfield, “but the result of this cat research was that there were a lot more open and WEP- encrypted hot spots out there than there should be in 2014.”

Updating an old hacking technique

In the 1980s, hackers looked for unprotected computers by “wardialing” — cycling through numbers with their modems. After the advent of Wi-Fi, “wardriving” saw hackers attaching an antenna to a car and driving through the city looking for weak and unprotected networks.

Bransfield says he built the “War Kitteh” collar for less than $100, and it became easier in the past months, when the Spark Core chip became easier to program, Wired reports.

Bransfield doesn’t own a cat. Coco is his wife’s grandmother’s cat.

In a three-hour walk through the neighborhood, Coco found 23 Wi-Fi hot spots, more than one-third of which were open to snoops with the simpler-to-crack WEP instead of the more modern WPA encryption.

Bransfield says many of the WEP connections were Verizon FiOS routers with their default settings left unchanged.